Project: Build you own spectroscope.
A spectroscope is an instrument used to break light up into its constituent colors, like a prism does, showing the light spectrum. Why would you want to do this?
A spectroscope is a device that lets us find out what things are made of. It works by taking light and splitting it up into its component colors. Different elements make different colors when they glow. We can make objects and gasses glow by heating them up in a flame, or by passing electricity through them. The spectroscope spreads out the colors of the light, and we can identify the elements by the bright lines we see in the spectroscope. (scitoys.com)
The video above shows you how to make one out of a cardboard tube, an old CD and some card-stock. This page from scitoys also describes a few variations on home made spectroscopes using similar materials found around the house.
How-To:
